A mold assembly (200) is described that includes an upper mold (4), a lower mold (5) and a plurality of adjusting members (7). The upper mold includes an upper mold core (42). The lower mold includes a lower mold carrier (51) and a lower mold core (52). The lower mold carrier includes a plurality of sidewalls (511), which cooperatively define an opening (512) and have a plurality of screw holes (515) defined therethrough in communication with the receiving cavity. The lower mold core is received in the receiving cavity with a clearance formed therebetween. The adjusting member engages in the screw holes for aligning the lower mold core with the lower mold carrier.